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From Mike Percy <mpe...@apache.org>
Subject Re: Spark Streaming + Kudu
Date Tue, 06 Mar 2018 07:52:11 GMT
Have you considered checking your session error count or pending errors in
your while loop every so often? Can you identify where your code is hanging
when the connection is lost (what line)?

Mike

On Mon, Mar 5, 2018 at 9:08 PM, Ravi Kanth <ravikanth.4b0@gmail.com> wrote:

> In addition to my previous comment, I raised a support ticket for this
> issue with Cloudera and one of the support person mentioned below,
>
> *"Thank you for clarifying, The exceptions are logged but not re-thrown to
> an upper layer, so that explains why the Spark application is not aware of
> the underlying error."*
>
> On 5 March 2018 at 21:02, Ravi Kanth <ravikanth.4b0@gmail.com> wrote:
>
>> Mike,
>>
>> Thanks for the information. But, once the connection to any of the Kudu
>> servers is lost then there is no way I can have a control on the
>> KuduSession object and so with getPendingErrors(). The KuduClient in this
>> case is becoming a zombie and never returned back till the connection is
>> properly established. I tried doing all that you have suggested with no
>> luck. Attaching my KuduClient code.
>>
>> package org.dwh.streaming.kudu.sparkkudustreaming;
>>
>> import java.util.HashMap;
>> import java.util.Iterator;
>> import java.util.Map;
>> import org.apache.hadoop.util.ShutdownHookManager;
>> import org.apache.kudu.client.*;
>> import org.apache.spark.api.java.JavaRDD;
>> import org.slf4j.Logger;
>> import org.slf4j.LoggerFactory;
>> import org.dwh.streaming.kudu.sparkkudustreaming.constants.SpecialN
>> ullConstants;
>>
>> public class KuduProcess {
>> private static Logger logger = LoggerFactory.getLogger(KuduPr
>> ocess.class);
>> private KuduTable table;
>> private KuduSession session;
>>
>> public static void upsertKudu(JavaRDD<Map<String, Object>> rdd, String
>> host, String tableName) {
>> rdd.foreachPartition(iterator -> {
>> RowErrorsAndOverflowStatus errors = upsertOpIterator(iterator, tableName,
>> host);
>> int errorCount = errors.getRowErrors().length;
>> if(errorCount > 0){
>> throw new RuntimeException("Failed to write " + errorCount + " messages
>> into Kudu");
>> }
>> });
>> }
>> private static RowErrorsAndOverflowStatus upsertOpIterator(Iterator<Map<String,
>> Object>> iter, String tableName, String host) {
>> try {
>> AsyncKuduClient asyncClient = KuduConnection.getAsyncClient(host);
>> KuduClient client = asyncClient.syncClient();
>> table = client.openTable(tableName);
>> session = client.newSession();
>> session.setFlushMode(SessionConfiguration.FlushMode.AUTO_FLU
>> SH_BACKGROUND);
>> while (iter.hasNext()) {
>> upsertOp(iter.next());
>> }
>> } catch (KuduException e) {
>> logger.error("Exception in upsertOpIterator method", e);
>> }
>> finally{
>> try {
>> session.close();
>> } catch (KuduException e) {
>> logger.error("Exception in Connection close", e);
>> }
>> }
>> return session.getPendingErrors();        ---------------------> Once,
>> the connection is lost, this part of the code never gets called and the
>> Spark job will keep on running and processing the records while the
>> KuduClient is trying to connect to Kudu. Meanwhile, we are loosing all the
>> records.
>> }
>> public static void upsertOp(Map<String, Object> formattedMap) {
>> if (formattedMap.size() != 0) {
>> try {
>> Upsert upsert = table.newUpsert();
>> PartialRow row = upsert.getRow();
>> for (Map.Entry<String, Object> entry : formattedMap.entrySet()) {
>> if (entry.getValue().getClass().equals(String.class)) {
>> if (entry.getValue().equals(SpecialNullConstants.specialStringNull))
>> row.setNull(entry.getKey());
>> else
>> row.addString(entry.getKey(), (String) entry.getValue());
>> } else if (entry.getValue().getClass().equals(Long.class)) {
>> if (entry.getValue().equals(SpecialNullConstants.specialLongNull))
>> row.setNull(entry.getKey());
>> else
>> row.addLong(entry.getKey(), (Long) entry.getValue());
>> } else if (entry.getValue().getClass().equals(Integer.class)) {
>> if (entry.getValue().equals(SpecialNullConstants.specialIntNull))
>> row.setNull(entry.getKey());
>> else
>> row.addInt(entry.getKey(), (Integer) entry.getValue());
>> }
>> }
>>
>> session.apply(upsert);
>> } catch (Exception e) {
>> logger.error("Exception during upsert:", e);
>> }
>> }
>> }
>> }
>> class KuduConnection {
>> private static Logger logger = LoggerFactory.getLogger(KuduCo
>> nnection.class);
>> private static Map<String, AsyncKuduClient> asyncCache = new HashMap<>();
>> private static int ShutdownHookPriority = 100;
>>
>> static AsyncKuduClient getAsyncClient(String kuduMaster) {
>> if (!asyncCache.containsKey(kuduMaster)) {
>> AsyncKuduClient asyncClient = new AsyncKuduClient.AsyncKuduClien
>> tBuilder(kuduMaster).build();
>> ShutdownHookManager.get().addShutdownHook(new Runnable() {
>> @Override
>> public void run() {
>> try {
>> asyncClient.close();
>> } catch (Exception e) {
>> logger.error("Exception closing async client", e);
>> }
>> }
>> }, ShutdownHookPriority);
>> asyncCache.put(kuduMaster, asyncClient);
>> }
>> return asyncCache.get(kuduMaster);
>> }
>> }
>>
>>
>>
>> Thanks,
>> Ravi
>>
>> On 5 March 2018 at 16:20, Mike Percy <mpercy@apache.org> wrote:
>>
>>> Hi Ravi, it would be helpful if you could attach what you are getting
>>> back from getPendingErrors() -- perhaps from dumping RowError.toString()
>>> from items in the returned array -- and indicate what you were hoping to
>>> get back. Note that a RowError can also return to you the Operation
>>> <https://kudu.apache.org/releases/1.6.0/apidocs/org/apache/kudu/client/RowError.html#getOperation-->
>>> that you used to generate the write. From the Operation, you can get the
>>> original PartialRow
>>> <https://kudu.apache.org/releases/1.6.0/apidocs/org/apache/kudu/client/PartialRow.html>
>>> object, which should be able to identify the affected row that the write
>>> failed for. Does that help?
>>>
>>> Since you are using the Kudu client directly, Spark is not involved from
>>> the Kudu perspective, so you will need to deal with Spark on your own in
>>> that case.
>>>
>>> Mike
>>>
>>> On Mon, Mar 5, 2018 at 1:59 PM, Ravi Kanth <ravikanth.4b0@gmail.com>
>>> wrote:
>>>
>>>> Hi Mike,
>>>>
>>>> Thanks for the reply. Yes, I am using AUTO_FLUSH_BACKGROUND.
>>>>
>>>> So, I am trying to use Kudu Client API to perform UPSERT into Kudu and
>>>> I integrated this with Spark. I am trying to test a case where in if any
of
>>>> Kudu server fails. So, in this case, if there is any problem in writing,
>>>> getPendingErrors() should give me a way to handle these errors so that I
>>>> can successfully terminate my Spark Job. This is what I am trying to do.
>>>>
>>>> But, I am not able to get a hold of the exceptions being thrown from
>>>> with in the KuduClient when retrying to connect to Tablet Server. My
>>>> getPendingErrors is not getting ahold of these exceptions.
>>>>
>>>> Let me know if you need more clarification. I can post some Snippets.
>>>>
>>>> Thanks,
>>>> Ravi
>>>>
>>>> On 5 March 2018 at 13:18, Mike Percy <mpercy@apache.org> wrote:
>>>>
>>>>> Hi Ravi, are you using AUTO_FLUSH_BACKGROUND
>>>>> <https://kudu.apache.org/releases/1.6.0/apidocs/org/apache/kudu/client/SessionConfiguration.FlushMode.html>?
>>>>> You mention that you are trying to use getPendingErrors()
>>>>> <https://kudu.apache.org/releases/1.6.0/apidocs/org/apache/kudu/client/KuduSession.html#getPendingErrors-->
but
>>>>> it sounds like it's not working for you -- can you be more specific about
>>>>> what you expect and what you are observing?
>>>>>
>>>>> Thanks,
>>>>> Mike
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Feb 26, 2018 at 8:04 PM, Ravi Kanth <ravikanth.4b0@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Thank Clifford. We are running Kudu 1.4 version. Till date we didn't
>>>>>> see any issues in production and we are not losing tablet servers.
But, as
>>>>>> part of testing I have to generate few unforeseen cases to analyse
the
>>>>>> application performance. One among that is bringing down the tablet
server
>>>>>> or master server intentionally during which I observed the loss of
records.
>>>>>> Just wanted to test cases out of the happy path here. Once again
thanks for
>>>>>> taking time to respond to me.
>>>>>>
>>>>>> - Ravi
>>>>>>
>>>>>> On 26 February 2018 at 19:58, Clifford Resnick <
>>>>>> cresnick@mediamath.com> wrote:
>>>>>>
>>>>>>> I'll have to get back to you on the code bits, but I'm pretty
sure
>>>>>>> we're doing simple sync batching. We're not in production yet,
but after
>>>>>>> some months of development I haven't seen any failures, even
when pushing
>>>>>>> load doing multiple years' backfill. I think the real question
is why are
>>>>>>> you losing tablet servers? The only instability we ever had with
Kudu was
>>>>>>> when it had that weird ntp sync issue that was fixed I think
for 1.6. What
>>>>>>> version are you running?
>>>>>>>
>>>>>>> Anyway I would think that infinite loop should be catchable
>>>>>>> somewhere. Our pipeline is set to fail/retry with Flink snapshots.
I
>>>>>>> imagine there is similar with Spark. Sorry I cant be of more
help!
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Feb 26, 2018 9:10 PM, Ravi Kanth <ravikanth.4b0@gmail.com>
wrote:
>>>>>>>
>>>>>>> Cliff,
>>>>>>>
>>>>>>> Thanks for the response. Well, I do agree that its simple and
>>>>>>> seamless. In my case, I am able to upsert ~25000 events/sec into
Kudu. But,
>>>>>>> I am facing the problem when any of the Kudu Tablet or master
server is
>>>>>>> down. I am not able to get a hold of the exception from client.
The client
>>>>>>> is going into an infinite loop trying to connect to Kudu. Meanwhile,
I am
>>>>>>> loosing my records. I tried handling the errors through getPendingErrors()
>>>>>>> but still it is helpless. I am using AsyncKuduClient to establish
the
>>>>>>> connection and retrieving the syncClient from the Async to open
the session
>>>>>>> and table. Any help?
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Ravi
>>>>>>>
>>>>>>> On 26 February 2018 at 18:00, Cliff Resnick <cresny@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>> While I can't speak for Spark, we do use the client API from
Flink
>>>>>>> streaming and it's simple and seamless. It's especially nice
if you require
>>>>>>> an Upsert semantic.
>>>>>>>
>>>>>>> On Feb 26, 2018 7:51 PM, "Ravi Kanth" <ravikanth.4b0@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Anyone using Spark Streaming to ingest data into Kudu and using
Kudu
>>>>>>> Client API to do so rather than the traditional KuduContext API?
I am stuck
>>>>>>> at a point and couldn't find a solution.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Ravi
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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